Powder trap



April 24, 1951 Filed Aug. 24, 1944 c. N. HICKMAN POWDER TRAP 2 Sheets-Sheet l Clarence N-H'1c1 man Wa-JPWWMM C. N. HICKMAN Aprii 24, 1951 POWDER TRAP 2 Sheets-Sheet 2 Filed Aug. 24, 1944 ammo/whom Clara-1:: N- Hickman from a shoulder projector.

Patented Apr. 24, 1951 POWDER TRAP Clarence N. Hickman, Jackson Heights, N. Y., assignor to the United States of America as represented by the Secretary of War Application August 24, 1944, Serial No. 551,047

9 Claims. (Cl. 6035.6)

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royaltythereon.

This invention relates to improved powder traps for trapping the propellant charge of rocket projectiles. In many forms of rocket pr,0 pelled projectiles the burning of the propellant powder must be completed within the projector tube, especially rocket propelled projectiles fired Therefore in order for the projectile toattain its maximum velocity within the projector tube the acceleration of such projectile. must be very rapid. This rapid acceleration however, forces the powder column contained within the projectile against the trap holding such propellant with considerable force thereby heavily overloading the powder trap. Furthermore the gas flow within the combustion chamber is extremely violent.

As the propellant material generally utilized in rocket projectiles is quite fragile the propellant is subject to fracture due to impact against the powder traps because of the sudden acceleration of the projectile, or due to the ending action of the gas flow. Any fracture of the propellant.

charge increases the burning area of such charge which results in a corresponding increase in the burning rate of the propellant. An increase in the burning rate of the propellant likewise causes a considerable increase in pressure within the projectile which could readily develop into adan- I gerously high chamber pressure. Further, the propellant material breaking away from the propellant charge tends to clog around conventional traps, which are generally located at nozzle of the projectile, thereby restricting the gas flow thru such nozzle, resulting in higher chamber pressures.

Accordingly it is an object of this invention to provide improved powder traps for a rocket projectile to securely hold the propellant charge of such projectile in such fashion as to prevent damage to the propellant charge due to the rapid acceleration forces of the projectile.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as'shown in the accompanying drawings in which:

Fig. l is a side elevational view of a rocket projectile partly in longitudinal section showin one form of trap for trapping cylindrical powder grains,

Fig. 2 is a cross-sectional view taken along the plane 2-2 of Fig. 1

Fig. 3 is'a fragmentary view of a rocket projectile in longitudinal section showing a modification of the trap rod illustratedin Fig. 1.

Fig. 4 is a longitudinal sectional view of a rocket projectile showing one form of a powder trap utilized to support the ribbon type of propellant material.

Fig. 5 is across-sectional view taken along the plane 5-5 of Fig. 4.

Fig. 6 is a fragmentary view similar to Fig. 4 but showing a modified form of trap for supporting ribbon type propellant material.

Fig. 7 is a view similar to Fig. 6 but taken along a plane disposed at right angles to the section shown in Fig. 6, namely, along the plane 1-1 of Fig. 6.

Fig. 8 shows a longitudinal sectional view of a rocket projectile embodying a trap similar to that illustrated in Fig. l but modified to trap very long cylindrical sticks of propellant material.

Fig. 9 is a cross-sectional view taken along the plane 99 of Fig. 7.

Referring to the drawings wherein similar characters refer to similar parts there is shown a rocket projectile comprisin mainly a cylindrical rocket motor I and a head 2. motor I is of hollow construction to house the propulsion charge of the projectile. One end of such rocket motor terminates in an integral nozzle 3 of the usual Venturi construction and a plurality of fins 2!! are secured about the exterior of the rear end of the motor I. Head 2 is secured I: to rocket motor I as by threads 4 and contains a pay load comprising an explosive charge or a chemical grenade. A rocket propellant charge 5 comprising a plurality of powder sticks 6 (Figs. 1 and 2) is suspended within rocket motor I in accordance with one modification of this invention by a trap rod 1. The trap rod 11 comprises a rod threaded at one end and the threaded end thereof is screwed into a threaded hole 8 in the base of'head 2. A plurality of radially disposed pins 9 as shown in Figs. 1 and 2, are suitably secured to the forward end of trap rod I. A transverse hole ID in the forward end of each powder stick 6 isprovided for mounting each of such sticks on pins 9. Thus powder sticks 6 are freely suspended longitudinally within rocket motor I while being firmly secured at the forward end of such sticks by the pins 9. Suspension of powder sticks 6 in the manner above described has been found to substantially eliminate fractures of the The rocket powder charge due to the rapid acceleration of a rocket projectile.

A modification of the trap rod above described is shown in Fig. 3. This type of construction is particularly well adapted to rocket projectiles having a nozzle l i of separate construction which is preferably fastened to rocket motor i by threads I2. A trap rod l3 shown in Fig. 3 is axially supported within rocket motor I by a spider lli welded to the rear end of trap rod l3. Spider 14 comprises a central hub having a plurality of radially disposed feet l5 which rest against the inside of nozzle ll in the throat portion thereof. A plurality of radially disposed pins 9 as shown in Figs. 1, 2 and 3, are likewise provided at the forward end of trap rod 13. Cylindrical powder grains 6 are similarly suspended from the pins a as previously described. With this form of construction, assembly of the propellant charge 5 is conveniently accomplished exteriorly of the rocket motor and on the trap rod prior to assembling the'nozzle ll to the rocket motor i.

Exceptionally long sticks of propellant material 6 can be conveniently trapped on a trap rod of the type shown in Figs. 1. 2 and 3 by providing properly supported within rocket motor I to prevent damage to such powder sticks due to rapid acceleration of the rocket projectile.

In Fig. 4 there is shown another modified form of powder trap. In this modification use is made of a ribbon type propellant material. Such material is cut into strips of suitable width from sheets of the propellant material. These strips are'placed about a transverse trap pin l6 mounted near the forward end of rocket motor 1 shown in Fig. 4. This form of trap is preferably used in a rocket construction wherein the nozzle 3 is integrally formed with rocket motor I but the head is readily detachable. The pin it is suitabl secured to the walls of rocket motor i. The ribbon propellant I1 is mounted on trap pin it prior to screwing the head 2 on to the forward end of rocket motor I. The first strip of ribbon propelv lant ll is'bent in the form of a hair pin and surrounds trap pin it as shown in Fig. 4 and preferably is the widest strip of propellant material placed within the rocket motor 5. Each successive strip placed on top of the first strip of ribbon propellant H is therefore successively smaller in width as shown in Fig. 5. A considerable number of such strips may be placed about trap pin it one on top of the other and this number is governed only by the thickness of each strip. ihe other governing factor, of course, is the weight of charge desired to propel the rocket projectile. As shown in Fig. 4 the length of each successive strip starting from the inner'strip may be of progressively shorter length so as to produce a tapered eifect as shown in Fig. 4. Thus a proper ratio between free port area to the web thickness of the propellant charge can be maintained.

To strengthen the propellant material i? where such material engages and is supported by pin lSa' sheet of cellulose tape [9 preferably of'a' type knownas Scotch Tape is interspersed between each ribbon of the propellant material 11 as shown in Fig. 4. The utilization of tape 4 it not only strengthens the propellant at this point but also serves to inhibit the combustion of such propellant material thereby substantially eliminating the possibility of the propellant breaking free from pin 16, due to too great a reduction in thickness of the propellant material combustion at this point.

With this form of trap the ribbon propellantis securely held against the acceleration forces of the rocket projectile and the walls of rocket motor I confine the rocket propellant charge within rocket motor i without appreciable side charge as shown in Fig. 6.

play.

A further modification of a powder trap for trapping the ribbon type of propellant charge shown in Fig. 4, is illustrated in Figs 6 and 7. The form of trap shown in such figures is preferably used with a detachable nozzle. The trap i 8 utilized in this type of construction comprises a rod bent into an inverted U-shape form or in the shape of a hair pin as shown in Fig. '7. Ribbons oi the propellant material ll are suspended from the top cross member of hair pin trap l8 and are stacked thereon as shown in the accompanying drawings. Each successive layer of the ribbon propellant is preferably of decreasing'width as shown in Fig. 9. Starting with the inside ribbon of propellant material each successive layer of propellant material may be somewhat shorter in length so as to provide a tapered Thus the proper ratio of free port area to the web thickness of the powder may be obtained. Cellulose tape l9 may be interspersed between the layers of propellant material ll about the transverse member of trap is for the purposes previously described. The trap l8 supporting the propellant charge comprising strips of ribbon propellant ll is inserted into the rocket motor I from the rear end thereof and the nozzle ii is then screwed into place. The two legs of trap .58 then bear on the sides of nozzle ll adjacent the throat thereof, thereby supporting the propellant charge as shown in the accompanying drawings.

Ignition of the propellant charge shown in any of the various modifications of powder traps is readily efiected by the use of any conventional rocket igniter. Any of the various modifications of rocket propellant traps for rocket projectiles disclosed herein secure the propellant charge against displacement and substantially eliminate fractures due to the rapid acceleration of the rocket projectile. Further, such devices are of simple construction and are readily assembled to the rocket projectile.

I claim:

l. A rocket motor comprising in combination a tubular member having a constricted exit passage at one end, a closure for said member at the other end, a propellant for said motor cornprising a plurality of cylindrical powder grains each having a transverse opening extending diametrically of said grain near an end thereof, and a plurality of radially divergent pins supported from said closure, each adapted to extend respectively through an opening in one of said grains for supporting said grains longitudinally within said member.

2. A rocket motor comprising in combination a tubular member having a constricted exit passage at one end, a closure for said member at the other end, a propellant for said member comprising a plurality of long cylindrical powder grains. each having a transverse opening near an end thereof, a rod centrally supported within said member and a plurality of equiangularly spaced'pin's extending radially of said rod ad jacent said closure, each pin extending respectively through the transverse opening of one of said grains to support said grains longitudinally a pin extending transversely thru said rod, arid-,1"

a propellant for said motor comprising a cylindrical "powder grain having a transverse opening extending diametrically of said grain, said propellant being supported within said tubularmember by said pin extending through said transverse opening.

4. A rocket motor comprising in combination a tubular member having an exit passage at one end, a closure for said member at the other end,

a rod centrally supported within said member, a plurality of pins extending transversely thru said rodand spaced in alignment along said rod, and a propellant for said motor comprising a cylindrical powder grain having a plurality of transverse openings along the length thereof,

said propellant being supported within f sa'i'd tubular member by cooperation of the transverse openings in said powder grain with the extending portions of said pins. I

5. A rocket motor comprising in combination a tubular member having at one end a constricted exit orifice, a support extending diametrical lyhpf said member near the end of said tubular mem her opposite said orifice, and a plurality of strips of ribbon-like propellant material drapedover said support to. hang longitudinally within said member.

6. A rocket motor comprising in combination propellant material at an area adjacent the pin about which said stack of sheet-like propellant material is draped.

7. A rocket motor comprising in combination a tubular member having at one end a constricted exit orifice, a closure for said member adjacent the other end, a U-shaped rod supported within said tubular member with the base portion of said rod adjacent said closure, and a plurality of strips of ribbon-like propellant material draped over said support to hang longitudinally within said member, each of said strips of propellant material decreasing successively in length and width.

8. A rocket motoricomprising in combination a housing defining a rearwardly opening combustion chamber, a, propellant supporting member having a forwardly facing propellant supporting surface, said propellant supporting member bein mounted in said combustion chamber near the forward end thereof, and an elongated unitary powder grain having a rearwardly facing supporting surface and positioned in said combustion chamber with its supporting surface in supporting relation to said first mentioned supporting surface and having the large bulk of its mass located rearwardly of said first mentioned supporting surface with a small part of its mass located forwardly thereof, whereby said powder grain is stressed substantially only in tension by set-back forces arising upon acceleration of a rocket embodying the motor.

9. In a rocket motor, the combination of a housing defining a rearwardly opening cylindrical combustion chamber, radially extending rodlike supporting means mounted near the forward end of said combustion chamber, and a propellant comprising a plurality of long grains of a powder composition each having an opening near an end thereof, said propellant grains being supported longitudinally in said chamber by said rod-like supporting means passing through said openings.

CLARENCE N. HICKMAN.

REFERENCES CITED Adelman Dec. 17, 1946 Skinner Aug. 10, 1948 Number 

